Matrix assembly

ABSTRACT

A method of forming a matrix assembly for use in forming creases or score lines in card-like material. The method comprises providing a steel strip, treating an upper surface of the steel strip with a resin adhesive, extruding one or more plastic material strips onto the metal strip to define a longitudinal channel and heating the assembly so formed to cure the resin adhesive and adhere the plastic material to the metal strip. The present method obviates the need to perforate the metal strip and therefore a thinner steel strip is obtained.

This invention relates to the scoring or creasing of card-like materialand, more particularly, relates to a method of manufacturing a matrixassembly for use in forming creases or score lines in card-likematerial, and to the matrix so formed.

Card-like material is creased to facilitate it being folded into itsfinal shape by pressing the material between a creasing rule of acutting and creasing press, and a creasing matrix. The creasing matrixcomprises a long flexible strip having a channel formed longitudinallytherein which is slightly wider than the creasing rule. The matrix stripis fastened to a press platen so that its channel is aligned with thecreasing edge so that on closing the press the rule edge urges theportion of the card comprising the crease into the matrix channel toprovide a well defined crease. In our European patent publication number0107490 there is disclosed a form of matrix assembly which is widelyused in cutting and creasing presses. The matrix generally comprises asteel strip onto which has been extruded one or more strips of plasticmaterial to define a channel running longitudinally of the strip, theplastic material being adhered to the strip by means of perforationsformed therein to which the plastic material can “key”.

Typically, the steel strips used in the above form of matrix are of oneof two thicknesses, 0.004″ and 0.006″. These thicknesses are required inorder to give adequate strength owing to the presence of perforations.This thickness of steel strip required a reduction in the height ofcreasing rules used in cutting and creasing dies. Clearly it would beadvantageous if a matrix could be formed of adequate strength which issufficiently thin so as not to require modification of the height of thecreasing rules of the cutting and creasing press.

The invention seeks to provide a method of forming a matrix, and amatrix so formed improved in the above respects.

According to a first aspect of the present invention, there is provideda method of forming a matrix assembly which comprises providing a steelstrip, treating the upper surface of the steel strip with a resinadhesive, extruding one or more plastic material strips onto the metalstrip to define a longitudinal channel and heating the assembly soformed to cure the resin adhesive and adhere the plastic material to themetal strip.

The invention further comprises a matrix strip assembly made inaccordance with the above method.

The method of the invention obviates the need to perforate the metalstrip and this leads to a number of advantages. Firstly, omitting theperforation step enables the matrix assembly to be produced morecheaply. Secondly, with there being no perforations present, it ispossible to use a thinner steel strip (for example, of thickness 0.002″)and still retain adequate strength. This means that no modification needbe made to the height of the creasing dies in a cutting and creasingpress.

The surface of the previous matrix strip was rough owing to the presenceof the perforations beneath the plastic, whereas the surface of thestrip in accordance with the present invention is smooth, and there istherefore no embossing of board or card creased therewith. Furthermore,delamination, which could be caused with the previous matrix assemblywhen the strip was cut or mitred at the point of a perforation, now nolonger occurs.

The absence of perforations also gives a longer running life and theplastic profile of the matrix assembly of the invention has an improvedfinish. Finally, waste is greatly reduced.

Preferably, the adhesive resin employed is a polyurethane or polyolefinresin. This is preferably applied to the surface of the steel strip in acontinuous manner immediately before the latter passes into an extrusiondie where the plastics material is attached thereto by extruding theplastic material profile onto the resin treated steel strip downstreamof the extrusion die in a process called external crosshead extrusion.The advantage of this method is that the steel strip is not undersignificant pressure from plastic material in the crosshead die,allowing the use of thinner (e.g. 0.002″) steel without deformation, andbecause of the fact that the strip freely passes through the crossheaddie, the tooling life is increased greatly. The plastic extrusions maybe controlled and guided into position externally of the crosshead dieby a series of horizontally and vertically micrometer adjustable heatedprecision rollers ensuring complete accuracy of size for both sides ofthe matrix, in respect of height, width and profile. Thereafter, theassembly passes to a heating zone to cure the adhesive resin and effectbonding of the matrix. Following this, the assembly is cooled, pulledoff and further assembled in-line with a double-sided pressure sensitiveadhesive tape to the bottom of the matrix, after which it is cut intosuitable lengths for packaging and onward transmission.

The plastic material adhered to the steel strip may be any suitableplastics material, but is preferably polypropylene. The metallicmaterial may also be any suitable metal, but is preferably steel. Thestrip may be conditioned and degreased before use, for example, using apropane torch or the like.

The invention will be described further, by way of example, withreference to the accompanying drawings, in which:

FIG. 1 is a schematic diagram illustrating the method of the invention;

FIG. 2 is a plan view of the die and adaptor on an enlarged scale;

FIG. 3 is a cross-section of the die and adaptor; and

FIG. 4 is a front elevation of the die.

Referring to the drawings, and in particular FIG. 1, a steel strip 10,which may have been pre-conditioned, is pulled between a haul offmechanism 12 and a brake mechanism 14. Between the latter devices it istreated in accordance with the invention as follows.

Firstly, the strip 10 enters a slot coat station 1 6 nowherepolyurethane or a polyolefin hotmelt resin is applied to its uppersurface. The strip 10 then passes-into the die 18 portion of an extruder20 where a polypropylene plastics material 22 is extruded onto the steelstrip 10 to form two parallel longitudinal strips 24,26 defining betweenthem a channel 28. The plastic extrusions may be controlled and guidedinto position externally of the crosshead die by a series ofhorizontally and vertically micrometer adjustable heated precisionrollers in a roller station 29 ensuring complete accuracy of size forboth sides of the matrix, in respect of height, width and profile

The assembly then passes into a heating unit 30 where the polyurethaneis cured, bonding the strips 24,26 to the metal strip 10 and forming thematrix assembly. The plastic material is preferably provided with ablowing agent, the latter helps stabilise the modified polypropylenepreferably employed, eliminating shrinkage of the plastics materialprofile. The temperature of the extrusion and polyurethane cure zone 30is preferably high, in the region of 250° C., to effect curing.

The assembly then passes into a cooling zone 32, preferably comprising avortex for rapid cooling. Further cooling may be provided, after whichthe assembly advances to the haul off winder unit 12. The matrix iscombined with a double-sided adhesive tape in a combining zone 34 wherethe tape is applied to the underside of the matrix strip 10. Thereafter,the matrix assembly may be encoded, cut into predetermined lengths andpackaged as is known per se.

The absence of perforations in the metal strip 1I enables a thinnerstrip to be used than was heretofore possible and the finished matrixassembly is therefore thinner, whilst still having adequate strength. Itcan therefore be used in standard cutting and creasing presses withouthaving to modify the cutter height.

1. A method of making a matrix assembly which comprises providing asteel strip (10), treating the upper surface of the steel strip with aresin adhesive, extruding one or more plastic material strips (24, 26)onto the metal strip (10) to define a longitudinal channel (28) andheating the assembly so formed to cure the resin adhesive and adhere theplastic material (22) to the metal strip.
 2. A method as claimed inclaim 1 wherein the adhesive resin employed is a polyurethane orpolyolefin resin.
 3. A method as claimed in claim 2 wherein the resin isapplied to the surface of the steel strip (10) in a continuous mannerimmediately before the latter passes into an extrusion die (18) wherethe plastics material (22) is attached thereto by extruding the plasticmaterial profile onto the resin treated steel strip downstream of theextrusion die.
 4. A method as claim in claim 1 wherein the plasticextrusions (22) are controlled and guided into position externally ofthe extrusion die by a series of horizontally and vertically micrometeradjustable heated precision rollers (29).
 5. A method as claimed inclaim 1 wherein after the plastics material is attached the assemblypasses to a heating zone (30) to cure the adhesive resin and effectbonding of the matrix.
 6. A method as claimed in claim 1 wherein aftercuring the resin the assembly is cooled (32), pulled off (12) andfurther assembly in-line (34) with a double-sided pressure sensitiveadhesive tape to the bottom of the matrix, and thereafter cut intosuitable lengths for packaging and onward transmission.
 7. A method asclaimed in claim 1 wherein the plastic material (22) adhered to thesteel strip is polypropylene.
 8. A method as claimed in claim 1 whereinthe metallic material is steel.
 9. A method is claimed in claim 8wherein the strip (10) is conditioned and degreased before use. 10.(canceled)
 11. A method as claimed in claim 3 wherein the resin isapplied to the surface of the steel strip (10) in a continuous mannerimmediately before the latter passes into an extrusion die (18) wherethe plastics material (22) is attached thereto by extruding the plasticmaterial profile onto the resin treated steel strip downstream of theextrusion die.
 12. A method as claim in claim 11 wherein the plasticextrusions (22) are controlled and guided into position externally ofthe extrusion die by a series of horizontally and vertically micrometeradjustable heated precision rollers (29).
 13. A method as claimed inclaim 12 wherein after the plastics material is attached the assemblypasses to a heating zone (30) to cure the adhesive resin and effectbonding of the matrix.
 14. A method as claimed in claim 13 wherein aftercuring the resin the assembly is cooled (32), pulled off (12) andfurther assembly in-line (34) with a double-sided pressure sensitiveadhesive tape to the bottom of the matrix, and thereafter cut intosuitable lengths for packaging and onward transmission.
 15. A method asclaimed in claim 14 wherein the plastic material (22) adhered to thesteel strip is polypropylene.
 16. A method as claimed in claim 15wherein the metallic material is steel.
 17. A method as claimed in claim16 wherein the adhesive resin employed is a polyurethane or polyolefinresin.
 18. A method is claimed in claim 17 wherein the strip (10) isconditioned and degreased before use.